Vitamin D shows promise but research still lagging

March 10, 2010|By Julie Deardorff, Tribune reporter

As far as Dr. Joseph Mercola is concerned, vitamin D is the magic bullet we've all been looking for. A lack of this wonder nutrient, the controversial natural health advocate said, can set the stage for no fewer than 33 disorders, including autism, cancer, diabetes and infertility.

"Vitamin D appears to reduce your risk of dying from virtually ANY disease," he wrote on his popular Web site. His recommendation? Get more sun, relax in a tanning bed or try supplements such as "Sunshine Mist," a vitamin D spray he sells.

Long ignored and feared in high doses, vitamin D is being hailed as the answer to nearly every health issue under the sun. The excitement stems from a flurry of preliminary studies finding links between vitamin D deficiencies and various illnesses, and this summer the federal Institute of Medicine plans to announce revised recommendations regarding dietary intake of vitamin D and calcium that almost certainly will be higher.

Despite the scientific attention being paid to vitamin D, experts caution that claims of wide-ranging health benefits are not yet supported by clinical evidence.

Though D is thought to hold tremendous promise, we've been down this garden path before: Hopes for the powers of vitamin E, beta carotene, antioxidant vitamins, selenium and other nutrients collapsed under the weight of rigorous, randomized clinical trials.

"It's premature to go out and make a big deal out of vitamin D supplementation when we don't have the evidence," said endocrinologist Anastassios Pittas, co-director of the Diabetes Center at Tufts University Medical Center in Boston. "We've been burned before on nutrition-based interventions," he said.

Yet already, bread, pasta, orange juice and soy foods are being fortified with vitamin D, and sales of vitamin D supplements grew 116.5 percent, from $108 million to $234 million, from 2007 to 2008, according to Nutrition Business Journal estimates.

The body naturally makes the vitamin when the sun's ultraviolet rays hit the skin, but fear of health risks and modern lifestyles have limited sun exposure for many.

Mercola, a non-practicing osteopathic physician who owns a clinic in Hoffman Estates, is one of the nutrient's most public and ardent supporters, with an evangelical style that can grate on the nerves of more cautious physicians.

Unlike most doctors, Mercola recommends universal baseline testing and widespread high-dose supplementation. "I've been preaching about this for a long time," said Mercola, who started his campaign 10 years ago. "Eventually the evidence comes out."

Mercola said children should get almost six times the amount of vitamin D recommended by the American Academy of Pediatrics, while adults and pregnant women should be receiving 5,000 International Units, or IUs, per day.

Most leading vitamin D researchers recommend no more than 1,000 to 2,000 IUs a day, citing insufficient evidence for higher doses. The federal guidelines, which are widely considered to be woefully inadequate, range from 200 to 600 IUs, depending on age.

"Dr. Mercola popularizes and promotes vitamin D in a very passionate way," said Dr. Gregory Plotnikoff, a senior consultant at the Center for Healthcare Innovation in Minneapolis who is conducting vitamin D trials. Mercola's high dosing recommendations "may be correct, but we need supportive data," he said.

Still, Plotnikoff and other researchers have high hopes for the vitamin, saying it could prove to be the single most cost-effective medical intervention in the U.S. today.

Best known for preventing rickets in children — the reason it is added to milk — vitamin D shines most in the role of absorbing calcium, which we need to form bones. A deficiency of vitamin D can contribute to osteoporosis by reducing calcium absorption.

Unlike vitamin E and others, vitamin D is a potent steroid hormone that has receptors in most, if not all, cells of the body. Mounting evidence suggests the so-called sunshine vitamin may also influence conditions unrelated to the skeleton, including cardiovascular disease, hypertension, diabetes, cancer, autoimmune disorders and mortality, said Dr. Michael Hollick, director of the Vitamin D, Skin and Bone Research Laboratory at Boston University School of Medicine.

"Vitamin D is as important for every cell in the body as thyroid hormone, estrogen and testosterone," said Plotnikoff. "These hormones turn on and off genes in our DNA. At least 1,000 key genes are under at least partial control by vitamin D. This was never the case for vitamin C, E and others."

Though observational studies have found a link between low vitamin D levels and an increased risk of disease, such an association doesn't prove a deficiency caused the problem. Low levels of D could also be a consequence of the illness.